Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, data, etc. The Universal Mobile Telecommunications System (UMTS) is a third generation (3G) cellular wireless technology developed by the 3rd Generation Partnership Project (3GPP). The UMTS standard supports various air interfaces or radio access technologies (RATs) such as Wide-band Code Division Multiple Access (WCDMA) and Time Division Synchronous Code Division Multiple Access (TD-SCDMA).
In a typical wireless network deployment, 3G technology is overlaid on top of existing second generation (2G) wireless technologies. For example, an urban area may have radio link coverage from both 2G (such as the Global System for Mobile Communication (GSM)) and 3G (such as TD-SCDMA) whereas there may be only 2G coverage beyond the core urban area. Mobile devices are required to perform measurements of available RATs to provide seamless service. A mobile device seeing good TD-SCDMA downlink channel quality and requesting a high data rate in a High-Speed Downlink Packet Access (HSDPA) operation may be allocated with increased or all available downlink timeslots for its downlink traffic, leaving no or insufficient idle time periods for a reliable inter-RAT measurement. When such a mobile device moves closer to TD-SCDMA-GSM cell boundary, the inability or delay in performing GSM measurement may lead to dropping an ongoing service such as a voice call when the mobile device goes out of TD-SCDMA cell coverage.